French diplomats said President Donald Trump's decision to withdraw all 2,000 US troops from the region had taken Paris by surprise.
France will keep troops in northern Syria for now because Islamic State militants have not been wiped out, contrary to the US view, and has started talks with the United States on the conditions and calendar of its withdrawal, officials said.
France is a leading member of the US-led coalition fighting militants in Syria and Iraq and has around 1,000 troops including special forces based in the north of the country, deployed alongside local Kurdish and Arab forces.
French diplomats told Reuters on Wednesday President Donald Trump's decision to withdraw all 2,000 US troops from the region had taken Paris by surprise. US officials justified the decision by saying Islamic State had been defeated.
"It shows that we can have different priorities and that we must count on ourselves first," Europe Minister Nathalie Loiseau told C-News television. "For now, of course we are staying in Syria because the fight against Islamic State is essential."
France is especially sensitive to the Islamic State threat after several major deadly attacks on its soil and officials believe the militant group continues to pose a threat. Hundreds of French nationals have joined the group in Syria.
In a statement, the foreign ministry said Paris and its coalition allies had started talks with Washington on the timeframe and conditions for the U.S withdrawal.
"The protection of the populations of northeastern Syria and the stability of this zone must be taken into account by the United States to avoid any new humanitarian drama and any return of the terrorists," it said.
It said Paris would be careful to ensure the security of all the U.S. partners in the area, including the Kurdish-dominated Syrian Democratic Forces, who fear an assault from Turkey.
President Emmanuel Macron spoke with Trump on Wednesday, diplomats said. In April, when Trump previously announced a U.S. withdrawal, Macron persuaded the U.S. leader that Washington should stay engaged by citing the threat of Iran in the region.
"Islamic State has not been wiped from the map nor have its roots. The last pockets of this terrorist organisation must be defeated militarily once and for all," Defence Minister Florence Parly said on Twitter..
French officials are scrambling to find out from U.S. agencies exactly what Trump's announcement means. The United States has been unclear on when the troops will be withdrawn.
"We’re used to it now with the Trump administration. The devil is in the detail," said a French diplomat.
France has about 1,100 troops as part of its Chammal operation against Islamic State. About 500 provide logistics, training and heavy artillery support with the remainder either working from Jordan, where most fighter jets take off to strike targets, vessels in the Mediterranean and Gulf or smaller contingents in the UAE, Qatar and Kuwait.
Its presence in Syria includes dozens of special forces, military advisers and some foreign office personnel.